This invention relates to the processing of biomaterials in general and more particularly to an improved method for finding metal traces in a biomaterial.
The importance of determining metal traces in organic materials, particularly foodstuffs, is increasing. As a rapid method for multielement analysis, the X-ray fluorescence analysis (RFA) is available. Without preceding enrichment of the metal traces, however, the sensitivity of this analytical method does not, in all cases, meet the more recent requirements of foodstuff control. In addition, the sample to be examined must be present in a form suitable for X-ray fluorescence analysis. For these reasons, a rapid method for the enrichment of metal traces and a sample presentation suitable for the analysis are prerequisites for the economical use of the X-ray fluorescence analysis in examining a large number of food samples.
The known chemical analysis and preparation techniques require a large amount of time for processing, e.g., breaking down, the necessary amounts of sample and are not reliable enough for the quantitative enrichment of metal traces. Thus, wet processing methods with oxidizing agents, for instance, require several hours for breaking down 20 g of meat and the sample solutions obtained are loaded with a large amount of foreign salts and their admixtures.
It is also known to process or break down biological materials with activated oxygen by the microwave process, cf. C. E. Gleit and W. D. Holland, Anal. Chem 34, (1962), p. 1454, in pure flowing oxygen, see also, for instance, B. Morsches, G. Toelg; Z. anal. Chem. 219 (1966), p. 61, or in pure oxygen at elevated pressure, see, for instance M. Berthelot, Ann. Chim. Phys. 26 (1892), p. 555. Heretofore, only quantities of up to about 1 g have been used. The quantitative processing (breakdown) of meat in pure oxygen at elevated pressure requires suitable communition and drying. The drying methods used so far in open systems involve the danger of metal losses due to volatilization. In drying in a closed system, the evaporated water must be separated from the sample, for instance, by condensation. Insufficient comminution of the sample and excessively high residual moisture of the sample cause incomplete processing, while a finely distributed, very dry material can lead to an explosion. For enriching metal traces, methods are known from the literature (see, for instance, R. Pueschel, Talanta 16, (1969), p. 351) which detect quantitites down to a few micrograms. All these methods are not directly applicable to the determination of metal traces in food either in the required short analysis time or with the desired sensitivity. Without appropriate preparation of the samples, traces of metallic poisons cannot be determined in biomaterials, for instance, with RFA, in the order of magnitude prescribed by laws (Hg: 0.000002%; Cd: 0.000008%, Pb: 0.00002% and As: 0.000005%).